Single coat non-stick coating system and articles coated with same

ABSTRACT

Single coat coating systems ( 22 ), as well as articles coated with such non-stick coating systems, are provided. The single coat system includes a fluoropolymer copolymer ( 14   a ), such as a fluoropolymer terpolymer including tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride monomers, which fluoropolymer copolymers are referred to collectively as THV. The single coat system exhibits excellent substrate adhesion and release properties, is resistant to separation failure at the interface between the binder ( 12 ) and fluoropolymer components ( 14   a ), and exhibits excellent adhesion to smooth substrates ( 16 ). The single coat system may also include a high level of fillers to provide increased damage resistance without compromising the above benefits.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention.

[0002] The present invention relates to non-stick coating systems whichare applied in single coats to the surface of a substrate to provide acoated substrate having a non-stick coating to which extraneousmaterials will not adhere. More particularly, the present inventionrelates to a single coat composition which provides excellent releaseproperties and excellent intracoat cohesion between the binder andfluoropolymer components thereof.

[0003] 2. Description of the Related Art.

[0004] Nonstick coatings have been well known for more than twentyyears. These coatings combine good adhesion to substrates such as metal,glass, or ceramics good cohesion for mechanical strength such asresistance to scratching and abrasion, and a low surface energy surfacethat is difficult to wet and resistant to adhesive attachment by othersubstances. Typically, these coatings include: 1) one or more highlyfluorinated polymers for nonstick properties, e.g.,polytetrafluoroethylene (PTFE), fluorinated ethylenepropylene (FEP) orperfluoroalkyl (PFA), and 2) one or more heat resistant binder resinsfor adhesion, e.g., polyamideimide (PAI), polyethersulfone (PES), orpolyphenylene sulfide (PPS), and 3) one or more pigments and fillers forcoloring or varied mechanical properties.

[0005] Nonstick coatings may be formulated for application and use inone layer or in multiple layers. In a one layer coating, all of theabove requirements must be achieved in a single coat. Therefore, sinceboth adhesion and nonstick properties must be obtained in the samelayer, the result is a compromise in performance. On the other hand, inthe multilayer coating, different layers provide different functions toachieve both good adhesion and mechanical strength and good nonstick orrelease properties. For example, a primer or first layer of a multilayercoating might contain all of the ingredients listed above, but with ahigh concentration of binder resin to promote adhesion, while a topcoator top layer of a multilayered coating might contain primarily afluoropolymer to provide the best nonstick surface. Therefore amultilayered coating with each layer specialized as to function may havea superior balance of adhesion and release properties compared to asingle layer coating where all properties must be achieved in the samelayer.

[0006] Primers for multilayer coatings and one layer coatings dependupon the same mechanism of film formation to realize their specificproperties. In both cases, the stratification of the ingredients isneeded to increase the concentration of binder resin at the substrate topromote adhesion, and to increase the concentration of fluoropolymerresin at the surface to improve nonstick properties or to provide asurface to which subsequent coats may be bonded by sintering. Over thecourse of the development of such coating systems, it has come to beaccepted that the adhesion of the primers to metal substrates is afunction of the amount of organic binder resin present at the interfacebetween the substrate and the coating. It is well known that organicbinders, such as polyamideimide, polyether sulfone and polyphenylenesulfide, for example, have excellent adhesion to metals.

[0007] Likewise, it has come to be accepted that the adhesion ofsubsequent layers or coats to the primer depends upon the amount offluoropolymer present at the interface between the primer and the nextlayer. This is due to the fact that adhesion between the primer andsubsequent layers is achieved by the fusing or sintering of thefluoropolymer in the primer to the fluoropolymer in the subsequent layerduring the curing process at temperatures above the melting point of thefluoropolymers.

[0008] A mixture of ingredients is expected, however, at both theprimer-substrate and the primer topcoat interfaces, because the primersthemselves include a mixture of ingredients. Some fluoropolymer willtherefore be present at the primer-substrate interface, and therebyadversely affect adhesion to the substrate, and some binder will bepresent at the primer-topcoat interface, and thereby adversely affectthe intercoat adhesion with subsequent layers. For these reasons, muchdevelopment effort has been directed to achieving a greater degrees ofseparation or stratification between the binder resin and thefluoropolymer in the primer, so that the binder moves to the bottom ofthe primer layer to increase substrate adhesion, and the fluoropolymermoves to the top of the primer layer to increase intercoat adhesion.Such differences in composition from top to bottom of the primer layerare known as “concentration gradients,” and are described in U.S. Pat.No. 4,087,394 to Concannon (1978) and in U.S. Pat. No. 5,240,775 toTannenbaum (1993).

[0009] The development of sharper concentration gradients in primers hasbecome more important with the increased emphasis on applying non-stickmulti-layered coatings to “smooth” substrates. Traditionally, metalsubstrates had been roughened by gritblasting or finishing (sanding)before application of a non-stick coating thereto. Application to“smooth” substrates eliminates the slow and expensive rougheningprocess. For purposes of the present application, a “smooth” substraterefers to a substrate that has been chemically cleaned and lightlyetched to an average roughness (Ra) of less than 100 microinches (2.5microns), and preferably of less than 50 microinches (1.25 micron). Byway of comparison, untreated rolled aluminum, for example, has anaverage roughness of 12-20 microinches (0.25-0.50 microns), andgritblasted aluminum has an average roughness of 160 to 220 microinches(4 to 5.25 microns).

[0010] A more recent direction in the development of primers is theinclusion of hard fillers to increase scratch and damage resistance. Theuse of such fillers is well known. and is also disclosed in U.S. Pat.No. 4,049,863 to Vassiliou (1977), noted above, in a range up to 20% byweight of the solids. More recent disclosures of the use of hard fillersmay be found in U.S. Pat. Nos. 5,250,356 to Batzer (1993) and 5,562,991to Tannenbaum (1996), wherein the amount of filler used is as high as35% by weight of the solid material.

[0011] In practice the main raw materials used in primers for non-stick,multi-layered coatings have not changed greatly in recent years. Thepreferred organic binder remains a polyamideimide (“PAI”) resin,prepared as an aqueous polyamic acid salt. The preferred fluoropolymerremains an aqueous dispersion of polytetrafluoroethylene (“PTFE”) resinwith a melt viscosity greater than 10³ poise. The recent improvements inthe performance of primers has come from (1) incrementally enhancing theoriginal, basic mechanism for promoting substrate adhesion and intercoatadhesion, viz., increasing the stratification of the primer through theaddition of fluoropolymers such as fluorinated ethylene propylene(“FEP”) that have lower melt viscosity and lower melting points thanPTFE, and (2) adding ever increasing amounts of hard fillers forimproved penetration and scratch resistance.

[0012] Adding hard fillers, while increasing the damage resistance ofthe primer, has the undesirable effect of adding an additionalingredient to the primer, which competes for space at the criticalprimer-substrate and primer-topcoat interfaces, and thereby detractsfrom the amount of preferred materials, as described above, which arerequired at the primer-substrate and primer-topcoat interfaces formaximum bonding.

[0013] Additionally, recent effort has been directed to the developmentof a single coat, non-stick coating system having fluoropolymer andbinder components, in which stratification between the fluoropolymer andbinder is allowed in order to enhance the substrate adhesion and therelease properties of the coating without failure between thefluoropolymer and binder components, and also, which coating hasexcellent adhesion to smooth substrates and allows the incorporation ofhigh levels of fillers thereinto for improved scratch and damageresistance.

[0014] As shown in FIG. 1, compensating for this loss of bond strengthby forcing greater separation/stratification of these materials has anobvious limit. In coating system 10, the stratification between binder12 and fluoropolymer 14 of primer 22 allows binder 12 and fluoropolymer14 to adhere well to substrate 16 and to topcoat 24, respectively.However, the large degree of stratification between binder 12 andfluoropolymer 14 actually creates, in effect, a new binder-fluoropolymerinterface 20. Specifically, the mechanical interconnection betweenbinder 12 and fluoropolymer 14 is minimal, and subject to failure, atbinder-fluoropolymer interface 20. Therefore, failure of coating system10 occurs within primer 22 itself, because the connection between theorganic binder and fluoropolymer (the intracoat cohesion) is amechanical interconnection, and prone to separation failure upon a largedegree of stratification within primer 22. The same type of failureillustrated in FIG. 1 may occur in conventional single coat non-stickcoating systems which include fluoropolymer and binder components.

[0015] What is needed is a single coat, non-stick coating system whichexhibits excellent substrate adhesion, yet is resistant to separationfailure at the interface between the binder and fluoropolymer componentsof the coating.

[0016] A further need is for a single coat, non-stick coating system,including a coating which allows for the incorporation into the coatingof a high level of fillers to provide increased damage resistance.

[0017] A still further need is for a single coat, non-stick coatingsystem, including a binder which has excellent adhesion to a smoothsubstrate.

[0018] A still further need is for a single coat, non-stick coatinghaving excellent substrate adhesion and release properties, yet which isresistant to separation failure at the interface between the binder andfluoropolymer components of the coating.

SUMMARY OF THE INVENTION

[0019] The present invention provides single coat, non-stick coatingsystems, as well as substrates coated with the non-stick coatingsystems. The single coat system includes a fluoropolymer, which is apolymer including a CF₂-CH₂ moiety in the polymer chain. An exemplaryfluoropolymer is a fluoropolymer copolymer, such as a fluoropolymerterpolymer including repeating monomers of tetrafluoroethylene (“TFE”),hexafluoropropylene (“HFP”), and vinylidene fluoride (“VDF”).Fluoropolymer copolymers including TFE, HFP, and VDF are collectivelyreferred to as “THV”. Further examples of such fluoropolymers arepolyvinylidene fluoride (“PVDF”) homopolymers, ethylenetetrafluoroethylene (“ETFE”) and HFP/VDF bipolymers, ethylenefluorinated ethylene-propylene (“EFEP”) terpolymers, and other possiblecombinations of ethylene and fluoroethylenic monomers.

[0020] The present inventors have found that a coating including THV maybe applied to a substrate in a single coat, the coating having excellentrelease properties and substrate adhesion, as well as excellentintracoat cohesion, or resistance to separation failure between thefluoropolymer and binder components. Further, the single coating may beapplied to smooth substrates, and may include a high level of fillers toprovide increased scratch and damage resistance without compromising theabove benefits.

[0021] In one form thereof, the present invention provides a singlecoat, non-stick coating system, including at least one binder resin(12), one binder resin including at least one of amide and aminefunctional groups; and at least one fluoropolymer resin (14 a), onefluoropolymer resin capable of reacting with at least one of the amideand amine functional groups of the binder resin.

[0022] In another form thereof, the present invention provides asingle-coat, non-stick coating system in the form of an aqueousdispersion, including a binder resin (12) including at least one ofpolyamideimide, polyamide, and polyimide; and a fluoropolymer resin (14a) including a copolymer of tetrafluoroethylene, hexafluoropropylene andvinylidene fluoride monomers.

[0023] In another form thereof, the present invention provides asubstrate (16) coated with a single coat, non-stick coating, thenon-stick coating including at least one binder resin (12), one binderresin including at least one of amide and amine functional groups; atleast one fluoropolymer resin (14 a), one fluoropolymer resin capable ofreacting with at least one of the amide and amine functional groups ofthe binder resin; and a filler material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention itself will be better understood by reference to thefollowing description of an embodiments of the invention taken inconjunction with the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention itself will be better understood by reference to thefollowing description of an embodiments of the invention taken inconjunction with the accompanying drawings, wherein:

[0026]FIG. 1 is a schematic illustration of a substrate surface having aknown coating composition adhered thereto, and a topcoat adhered to thecoating;

[0027]FIG. 2 is a schematic illustration showing a substrate having asingle coat, non-stick coating system in accordance with the presentinvention adhered thereto, and further showing a topcoat adhered to thecoating system:

[0028]FIG. 3 is a perspective view of a test apparatus for carrying outthe mechanical scratch adhesion test of Test Method A, which is setforth in Appendix A;

[0029]FIG. 4 is a perspective view of an apparatus for carrying out theresistance to mechanical damage by knife cutting and scraping test ofTest Method B, which is set forth in Appendix B; and

[0030]FIG. 5 is a schematic illustration showing the cutting andscraping action of a blade of the testing apparatus of FIG. 4 upon asubstrate surface.

[0031] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate preferred embodiments of the invention, and suchexemplifications are not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION

[0032] The present invention provides a single coat non-stick coatingsystem. The single coat system includes a fluoropolymer, which is apolymer including a CF₂-CH₂ moiety in the polymer chain. An exemplaryfluoropolymer is a fluoropolymer copolymer, such as a fluoropolymerterpolymer including three repeating monomer units, specifically, eachof tetrafluoroethylene (“TFE”), hexafluoropropylene (“HFP”), andvinylidene fluoride (“VDF”) units. Fluoropolymer copolymers includingTFE, HFP, and VDF monomers are collectively referred to as “THV”. Onesuitable THV terpolymer is Dyneon® E-15851, available from Dyneon LLC,8744 33^(rd) Street North, Oakdale, Minn., 55128, a 3M Company. (Dyneon®is a registered trademark of Dyneon LLC).

[0033] Further examples of such fluoropolymers are polyvinylidenefluoride (“PVDF”) homopolymers, ethylene tetrafluoroethylene (“ETFE”)and HFP/VDF bipolymers, ethylene fluorinated ethylene-propylene (“EFEP”)terpolymers, and other possible combinations of ethylene andfluoroethylenic monomers.

[0034] The fluoropolymer may have a melting point of about 220° C. orabove, however, fluoropolymers having melting points between about 160°C. and about 250° C. are also suitable.

[0035] The present non-stick coating system may be applied to a widevariety of substrates, including but not limited to, metal cookware,printer and photocopier rollers, building materials, industrial tools,and high temperature resistant fabrics such as fiberglass and wovenpolyaramids.

[0036] Improving the connection between the binder and the fluoropolymerallows for sufficient stratification in the coating between the binderand fluoropolymer for improved substrate adhesion and release property,yet also allows the retention of the intracoat cohesion between thebinder and fluoropolymer within the coating. Improving such connectionman be accomplished by: (1) improving the wetting of the fluoropolymerby the binder, and (2) by creating a chemical bond, as opposed to amechanical interconnection, between the binder and the fluoropolymer.

[0037] The present inventors have found that the addition of the THVterpolymer to a single coat composition including a binder provides acoating having excellent substrate adhesion and release properties andwhich is resistant to separation failure between the fluoropolymer andbinder components. It is believed that THV accomplishes theseimprovements because (1) the VDF monomer in the THV terpolymer providesa slight increase in the surface energy of the fluoropolymer to therebyincrease the wetting and adhesive contact with the binder, asdemonstrated in Examples I, II(A), and II(B), and (2) the VDF monomerprovides a reactive site that creates a chemical bond between the THVterpolymer and binder resins which include terminal amine and amidegroups.

[0038] Regarding (1) above, the ability for the fluoropolymer and binderto be wetted onto one another, such that the binder and fluoropolymerare in intimate adhesive contact, is a function of the surface energiesof the binder and fluoropolymer. Ideally, the surface energies of thebinder and the fluoropolymer are substantially equal, to maximize thewetting therebetween. Because fluoropolymers have low surface energies(typically less than 25 dynes/cm), a significant difference in surfaceenergies typically exists between the binder and the fluoropolymer,inhibiting the wetting therebetween. It is believed that the VDF monomerin the THV terpolymer provides a slight increase in the surface energyof the THV terpolymer, which in turn provides a corresponding decreasein the difference in surface energies between the THV terpolymer and thebinder to improve the wetting therebetween, as demonstrated in ExamplesI, II(A), and II(B).

[0039] In fact, as shown in Examples I, II(A), and II(B), the improvedwetting between THV and the binder resin provides such sufficientattachment therebetween that a single coat non-stick coating compositionincluding THV demonstrates superior substrate adhesion, releaseproperties, and intracoat cohesion to known compositions, even without abinder which does not include terminal amine or amide groups, such aspolyether sulfone (“PES”). The benefit of including THV in a coatingcomposition having a binder with terminal amine or amide groups isdescribed below.

[0040] Regarding (2) above, the ability of THV to form chemical bondswith terminal amine and amide groups increases the intracoat cohesionbetween THV and binders which include terminal amine and amide groups,such as polyamideimide (“PAI”). This is type of bonding is illustratedby the well known chemistry associated with the vulcanization of THVelastomeric polymers, such that described in literature available fromthe 3M Company for use with its Fluorel® Fluoroelastomers. (Fluorel® isa registered trademark of Minnesota Mining and Manufacturing Co.). Forexample, such polymers undergo chemical crosslinking with diamines bythe following reactions:

[0041] The amine functionality shown above in reactions (1) and (2) forterminal amine groups is also available for the amide groups of the PAIresin.

[0042] This improved intracoat cohesion in a primer for a multicoatsystem, which primer includes the THV terpolymer and a binder havingterminal amine and amide groups, is schematically illustrated in FIG. 2,wherein a large degree of stratification between binder 12 andfluoropolymer 14 a, which includes THV, is allowed, to maximizeprimer-substrate and primer-topcoat adhesion, while maintaining strongintracoat cohesion within primer 22 a between binder 12 andfluoropolymer 14 a via the chemical bonding between binder 12 andfluoropolymer 14 a, shown at 20 a.

[0043] The fluoropolymers may comprise approximately 15 to 60% by weightof the solid content of the coating composition, wherein approximately 5to 100% by weight of the fluoropolymers are capable of reacting with theamide and amine functional groups of the binder resin. Suchfluoropolymers may have a melt viscosity of 10³ to 10⁶ poise.Additionally, the fluoropolymer capable of reacting with the amide andamine functional groups of the binder resin may include 5-30% by weightvinylidene fluoride (—CH₂—CF₂—) therein. The foregoing fluoropolymersmay also be blended with other fluoropolymers such aspolytetrafluoroethylene (“PTFE”), fluorinated ethyleneproylene (“FEP”)and perfluoroalkyl (“PFA”).

[0044] Binder resins may include polyester, polyamide, polyamideimide,polimide, polyether sulfone, polyphenylene sulfide, polyether etherketone, silicone, epoxy, and acrylic resins, and blends of theforegoing. The binder resins comprise approximately 25 to 65% by weightof the solid content of the coating composition, and approximately 20 to100% by weight of the binder resin may include a resin with amide and/oramine functional groups.

[0045] Fillers may include inorganic metal oxides and metal oxidecomplexes, such as titanium dioxide, chromium dioxide, zinc oxide, ironoxide, aluminum oxide, silicon oxides, zirconium oxide, and mixtures ofthe foregoing; silicates, such as aluminum silicate, magnesium aluminumsilicate, and mixtures of the foregoing; and inorganic carbides andnitrides, such as silicon carbide, titanium carbide, silicon nitride,titanium nitride, and boron nitride, and mixtures of the foregoing.

[0046] Pigments may include ultramarine blue zeolite, channel black,carbon black, and mixtures of the foregoing. The pigments and fillersmay comprise from 0 to 45% by weight of the solid content of the coatingcomposition.

[0047] The substrate may consist, for example, of stainless steel,carbon steel, or aluminum, which is smooth or which has been chemicallyetched or mechanically roughened by gritblasting or abrasion with gritimpregnated pads, cloth, or paper to an average surface roughness of 0.5μm to 2 μm (20-80 microinches) Ra, or alternatively, 2 μto 5 μm (80-200microinches) Ra.

EXAMPLES Example 1 Comparison of Damage Resistance Between CoatingsHaving Varying Proportions of THV and PTFE Fluoropolymer Resins

[0048] Mixtures of high temperature resistant organic binders withfluoropolymers and fillers were prepared, with the binders andfluoropolymers present at a fixed ratio with respect to each other. Themixtures were prepared from a base containing an aqueous solution ofpolyamide imide resin into which had been dispersed by ball milling apolyethersulfone (“PES”) resin, as well as pigments and fillersincluding finely divided alunina, ultramarine blue and carbon blackpigments. To this base was added in varying proportions an aqueousdispersion of PTFE and an aqueous dispersion of THV fluoropolymerterpolymer resin containing reactive vinylidene fluoride monomers. Thecoatings were formulated in such a way that the total amount offluoropolymer to other ingredients was held constant while the ratio ofone fluoropolymer to the other was varied. The composition of the solidingredients in the coatings by weight was as follows: TABLE IFormulations of coatings with varying proportions of PTFE and THV.Coating Number 1 2 3 4 5 6 Polyamideimide resin 22 22 22 22 22 22Polyethersulfone resin 6 6 6 6 6 6 Polytetrafluoroethylene resin 42 4038 33 16 0 Terpolymer of TFE/HFP/VdF 0 2 4 9 26 42 Carbon Black pigment2 2 2 2 2 2 Aluminum Oxide (Fine 15 15 15 15 15 15 Particle Size) ZincOxide 1 1 1 1 1 1 Ultramarine Blue pigment 12 12 12 12 12 12 Total 100100 100 100 100 100

[0049] Test panels were prepared for each coating using 7″×7″×0.063″panels of 3003 aluminum alloy. The test panels were prepared bychemically cleaning and etching in a commercial dishwasher. The panelswere exposed first to one six minute washer cycle using a solution of 5%sodium hydroxide at ˜65° C., followed by a deionized water rinse and asecond six minute cycle using 1% nitric acid at ˜65° C., followed by adeionized water rinse and drying. This treatment produced a clean,smut-free surface with an average roughness of ˜30 microinches (0.75micron).

[0050] Each coating was applied to a respective panel by spraying to adry film thickness of 15-20 μm, and was cured for 5 minutes at 400° C.metal temperature. The panels were tested for 30 minutes using themechanical scratch tester as described in Test Method A, as set forth inAppendix A. The results were as follows: TABLE II Mechanical scratchtest results of the coatings of Table I. Coating Number 1 2 3 4 5 6Scratch adhesion result, 10 = best 1 4.5 5 5.5 4.5 4

[0051] The results indicate that even a small amount of the THVterpolymer improves the damage resistance of the coating.

Example II(A) Comparison of Binder-fluoropolymer Intracoat CohesionBetween Coating Compositions Respectively Containing FEP and THVFluoropolymers

[0052] Two coating compositions were prepared, each including a binderof polyether sulfone (“PES”) dissolved in N-methyl pyrrolidone andxylene. In one, fluorinated ethylene-propylene (“FEP”) powder wasdispersed, and in the other, a powder of THV terpolymer was dispersed,both at a ratio of 75% PES and 25% fluoropolymer by weight. The coatingswere colored equally with an inorganic pigment as an aid to inspection.The coatings were then sprayed onto respective aluminum panels to a dryfilm thickness of 20 microns, and then cured for 5 minutes at 400° C.

[0053] Mixtures of polyethersulfone (PES) resin were prepared with aninorganic pigment and either: (1) a powder form of a fluorinatedethylenepropylene “FEP” fluoropolymer (a copolymer oftetrafluoroethylene and hexafluorofluoropropylene) or (2) a powder formof the THV fluoropolymer terpolymer described above. The mixtures weremade by dissolving the PES resin in a blend of N-methylpyrrolidone andxylene and dispersing a mixed metal oxide green pigment (Shephard #223Green) into the resin solution by bead milling. The two powders wereadded by mixing and bead milling to achieve a suitable dispersion andsmoothness. The composition of the solid ingredients in the two mixturesby weight was as follows: TABLE III Formulations of coatings withvarying proportions of FEP and THV. Coating Number 1 2 PES  42  42 FEP 0  33 Terpolymer of TFE/HFP/VdF  33  0 Inorganic Green pigment  25  25Total 100 100

[0054] The mixtures were sprayed onto aluminum “Q” Panels, prepared asdescribed above in Example I, to a dry film thickness of 20 μand cured 5minutes at 400° C.

[0055] On inspection, the coating containing FEP had a heavy waxysurface layer that could be removed with a fingernail down to a glossylower layer. This indicated a sharp separation/stratification of theorganic binder and FEP, as well as a loss of intracoat cohesion betweenthe binder and fluoropolymer within the dried film. In contrast, thecoating with the terpolymer fluoropolymer resin showed no removable waxysurface layer and excellent intracoat cohesion between the binder andfluoropolymer. This observation demonstrates the improved compatibilityof the terpolymer resin compared to a higher fluorinated, butnon-reactive fluoropolymer resin.

Example II(B) Comparison of Amount of Fluoropolymer Present at theSurface Thereof, Between Coating Compositions Respectively ContainingFEP and THV Fluoropolymers

[0056] In a second experiment, one coated panel was prepared using eachof the above coatings in the manner described above in Example II(A). Acyanoacrylate glue was applied between the coated panels. The panelswere clamped together for several minutes to cure the glue, and aftercuring the panels were forced apart. The glue completely released fromthe coating containing the terpolymer flurorpolymer resins, while glueresidue was observed remaining on the surface of the FEP-containingcoating. This result indicates that the amount of fluoropolymer at thesurface of the terpolymer resin coating was equal to or greater than theamount of fluoropolymer at the surface of the FEP coating and therelease properties of the former were superior to the latter.

Example III Preparation and Physical Testing of Coating CompositionsRespectively Containing FEP and THV Fluoropolymers used as Primer

[0057] Primers were prepared using mixing processes typical of coatingsmanufacturing operations. An aqueous solution of Torlon AI-10, polyamideimide resin, was first prepared by dissolving the resin in a mixture ofN-methyl pyrrolidone (“NMP”), furfuryl alcohol, dimethylamine ethanol(“DMAE”), and wetting agents/surfactants in water, in a manner similarto that described in U.S. Pat. No. 4,049,863 to Vassiliou. Fillers weredispersed in this solution, and two portions of the solution were thenblended with respective aqueous dispersions of the FEP and THVfluoropolymers. The primer formulations are set forth in Table IV below,which table sets forth the composition of the “wet”, or liquid phase,primer before application of the primer to the substrate followed bycuring: TABLE IV Formulations of primers respectively including THV andFEP. Primer 1 Primer 2 Binder Resins: Torlon AI-10 Polyamideimide Resin 7.5  7.5 Fluoropolymers Resins: Daikin D-3B PolytetrafluoroethyleneDispersion  6.6  6.6 Dyneon THV E-15851 Dispersion  3.4 — Daikin ND-1FEP Dispersion —  3.4 Other Solid Ingredients Norton E-330 AluminumOxide (Alumina)  4.0  4.0 Ferro RB-30 Untramarine Blue Pigment  2.7  2.7Zinc Oxide  0.1  0.1 Channel Black Pigment  1.0  1.0 Other Water  66.0 66.0 NMP  4.0  4.0 Furfuryl alcohol  1.5  1.5 DMAE  1.5  1.5 AirProducts Surfylol 440  1.0  1.0 Triton X-100  0.7  0.7 Total 100.0 100.0

[0058] Rolled aluminum (alloy 1100) disks, ˜7″ in diameter and 0.635″thick, were prepared by chemically cleaning and etching in a commercialdishwasher. The disks were exposed first to one six minute washer cycleusing a solution of 5% sodium hydroxide at ˜65° C., followed by adeionized water rinse and a second 6 minute cycle using 1% nitric acidat ˜65° C. followed by a deionized water rinse and drying. Thistreatment produced a clean, smut-free surface with an average roughnessof ˜30 microinches (0.75 micron). The primer compositions given asPrimer 1 and Primer 2 above were sprayed onto respective ones of thedisks. The primers were applied to a dry film thickness of 8-10 micronsand dried for 2 minutes at 95° C. to produce a coating that was dry tothe touch.

[0059] Following drying, a topcoat of a composition similar to thatdescribed in U.S. Pat. No. 4,049,863 to Vassiliou was sprayed onto thedisks at a dry film thickness of 18-20 microns. The disks were dried for2 minutes at 95° C., and cured for 5 minutes at 430° C. to produce asmooth, glossy black non-stick coating.

[0060] The disks were subject to various tests to evaluate the adhesionand durability of the coating systems. Disks with both Primer 1 andPrimer 2 had excellent resistance to knife scratching and excellentadhesion when subjected to cross hatching and boiling in water for 15minutes.

[0061] Further, both had similarly good scratch resistance whenevaluated by a mechanical scratch tester as described in Test Method A,as set forth in Appendix A hereto. Test method A simulates thescratching action of a fork, and is a measure of resistance of thecoating to penetration by a sharp point.

[0062] However, there were significant differences found when the diskswere evaluated by a mechanical knife scratch tester as described in TestMethod B, as set forth in Appendix B hereto. Test method B simulates thescraping action of a spatula and the cutting action of a knife blade,wherein ratings may be applied thereto based on the observed results(which ratings are set forth in Test Method A). In this test, asignificant portion of the topcoat applied over Primer 2 was scrapedoff, resulting in a rating of about 6, while the topcoat applied overPrimer 1 remained almost entirely intact, resulting in a rating of about9. This demonstrates both (1) the improved adhesion between Primer 1 andthe topcoat (intercoat adhesion) and (2) the improved cohesion withinthe Primer 1 itself (intracoat cohesion) over Primer 2, where Primer 1includes the THV and Primer 2 includes FEP.

Example IV Preparation and Physical Testing of a Coating CompositionContaining THV, and a Combination of Polyamideimide and PolyetherSulfone Resins, Wherein the Coating is used as Primer

[0063] A primer composition including THV was prepared in accordancewith the procedure set forth in Example III above, wherein part of thepolyamideimide organic binder resin was replaced with polyether sulfone.The primer formulation is set forth in Table V below, which table setsforth the composition of the “wet”, or liquid phase, primer beforeapplication to a substrate followed by curing: TABLE V Formulation of aprimer containing THV and a combination of polyamideimide and polyethersulfone resins. Examples Primer 3 Binder Resins: Torlon AI-10Polyamideimide Resin  6.0 Radel A700X Polyether Sulfone Resin  1.5Fluoropolymers Resins: Daikin D-3B Polytetrafluoroethylene Dispersion 6.6 Dyneon THV E-15851 Dispersion  3.4 Daikin ND-1 FEP Dispersion —Other Solid Ingredients Norton E-330 Aluminum Oxide (Alumina)  4.0 FerroRB-30 Untramarine Blue Pigment  2.7 Zinc Oxide  0.1 Channel BlackPigment  1.0 Other Deionized water  66.0 N-methyl pyrrolidone (NMP)  4.0Furfuryl alcohol  1.5 Dimethylamino ethanol (DMAE)  1.5 Air ProductsSurfylol 440 (surfactant)  1.0 Triton X-100 (surfactant)  0.7 Total100.0

[0064] Prior to adding to the formula, the polyether sulfone resin wasground by ball milling for 72 hours in a water slurry until it wasreduced in particle size to less than 15 microns average. The aboveprimer formula was coated onto aluminum disks prepared as describedabove in Example III, and a topcoat was applied thereto, again asdescribed above in Example III. The resulting coating system includingPrimer 3 had adhesion and scratch resistance, as measured by TestMethods A and B, respectively, which were superior to Primer 1, andadditionally, Primer 3 had better flexibility than Primer 1.

[0065] Although several broad examples which incorporate the presentinvention have been described above, it is to be understood that thepresent invention is not to be limited by the examples disclosed herein.Indeed, the disclosure and examples above teach one of ordinary skill avirtually limitless number of conditions which would be within the scopeof the claims appended hereto.

[0066] Further, while this invention has been described as having apreferred design, the present invention may be further modified withinthe spirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims. application istherefore intended to cover any variations, uses, or adaptations of theinvention using its general principles. Further, this application isintended to cover such departures from the present disclosure as comewithin known or customary practice in the art to which this inventionpertains and which fall within the limits of the appended claims.

APPENDIX A Test Method A Mechanical Scratch Adhesion

[0067] 1. Scope:

[0068] Coatings for cookware are susceptible to abuse and damage byscratching and cutting with metal utensils. Resistance to this kind ofdamage is often measured by a so called “Tiger Paw” test. In this test,a device equipped with ball point pen tips is used to stir food cookingin a piece of coated cookware. The pen points simulate damage by metalutensils, and provide a convenient renewable test implement. However,the “Tiger Paw” test is long in duration, difficult to control andsubjective to evaluate.

[0069] Test Method A describes a procedure and apparatus that inflictssimilar abuse on coatings, yet is reproducible, objective and quick. Asshown in FIG. 3, test apparatus 30 a includes weighted ball point pentip 32 affixed to balance arm 34, where pen tip 32 is placed on coatedsubstrate surface 36 which is revolving on turntable 38. At the sametime, balance arm 34 oscillates from side to side by means of revolvingcam 40. Turntable 38 and cam 40 are driven by constant speed DC motors42. The speed of turntable 38 and cam 40 are controlled by variable DCpower supplies. The amplitude of oscillation is controlled by the degreeof eccentricity in cam 40. Weight 44 is variable. By adjusting thespeeds of motors 42 and the amplitude of oscillation of balance arm 34,various scratch patterns may be obtained. These can be adjusted to covera small or large surface area.

[0070] To further simulate the conditions encountered by coatings fornon-stick cookware, test piece 50 (panel or pan) is covered with hot oil51. The temperature of oil 51 is maintained with IR heat lamps 52 and ismonitored with a thermometer or thermocouple (not shown).

[0071] 2. Equipment and Materials:

[0072] 2.1 Mechanical scratch adhesion apparatus 30 a with set ofweights 44.

[0073] 2.2 Ball point pen tip 32, such as Paper Mate medium pointstandard refill cartridges or equivalent.

[0074] 2.3 Hot plate

[0075] 2.4 Cooking oil 51

[0076] 2.5 Thermometer or digital read out with thermocouple wire

[0077] 2.6 Small clips 53

[0078]2.7 Shallow pan approximately 10 inches (25 cm) in diameter.

[0079] 2.8 Set (2 or 3) of 250 watt infrared heating lamps 52 on stands.

[0080] 3. Procedure:

[0081] 3.1 Check the balance and level of balance arm 34 with test piece50 in position. Adjust if necessary. Remove test piece 50. Set theamplitude of the oscillation by choosing the proper cam setting. Set theminimum and maximum radius by loosening the balance arm retaining screw(not shown) and adjusting at the extremes of cam 40. Usually, a centercircle of about 2 inches is allowed in the test pattern.

[0082] 3.2 Without weight on balance arm 34, and holding pen 32 aboveturntable 38, adjust the speed of turntable 38 and cam 40. Typically,cam 40 moves at a rate of 0 to 3 times faster than turntable 38.

[0083] 3.3 Place a piece of paper on turntable 38 and hold in place withtape. Load pen 32 with a light weight 44 (approx. 200 grams.) Place pen32 on the paper and allow to trace the scratch pattern it will follow.Save the pattern. This is also a check of the functioning of pen 32. Ifpen 32 does not write, replace it.

[0084] 3.4 Remove paper. Center test piece 50 on turntable 38. (Iftesting panels (not shown), place test piece 50 on turntable 38 andplace panels in test piece 50. Panels must be of a size large enough toaccommodate the size of the scratch pattern). Using clips 53, anchortest piece 50 to turntable 38. Holding pen 32 above test piece 50, turnon turntable 38 and cam 40 and observe several revolutions to ensurethat the scratch pattern is entirely on test piece 50. Turn off motor42.

[0085] 3.5 Heat sufficient cooking oil 51 to cover test surface by about¼ inch. Heat to test temperature. (CAUTION: Above about 150° C., cookingoils 51 emit fumes and strong odors. Also, they become quite flammable.If running over 150° C., conduct test in a well ventilated area,preferably in a fume hood.) Pour hot oil 51 into test piece 50. PositionIR lamps 52 close to test piece 50 and turn on to maintain temperatureof oil 51. Some pre-testing of the proper position of lamps 52 will berequired to maintain the temperature within a range of ±5° C. Monitorevery 5 minutes during test, and adjust position of lamps 52 to holdthis tolerance. (A continuously reading temperature gauge is mostconvenient for this measurement.)

[0086] 3.6 Place a proper weight 44 on balance arm 34. Typically, thiswill vary from 250 to 1000 grams. Start both motors 42 and place pen 32gently on coated surface 36. Allow the test to run for the requiredlength of time.

[0087] 4. Evaluation:

[0088] 4.1 Record the following information: (1) speed of turntable 38and cam 40 in rpm; (2) cam amplitude setting (number or distance frominside to outside radius in cm); (3) load on pen point 32 in grams; (4)temperature of oil 51; (5) duration of test; and all test pieceparameters (substrate and substrate preparation, coating, thickness,cure, etc.).

[0089] 4.2 Remove test piece 50, drain oil 51, and wash in warm waterand mild detergent. Blot dry with paper towel. Visually observe thedamage to the coating surface 36. This may be done on a comparativebasis against other test specimens, or may be rated on the scale setforth below. In general, performance levels have been rated as follows:TABLE VI Performance levels 10 No effect Light scratching of thesurface. No break through at any place in the scratch pattern.  8 SlightLight scratching of the surface. Inner circle of pattern is cut throughto metal 100%. Outer circle cut through to metal <50%.  6 ModerateModerate scratching between inner and outer circle. Inner and outercircle both cut through to metal (inner usually worse that outer.) Atthis point begin inspecting and noting adhesion loss between coats or tosubstrate.  4 Considerable Less than 25% loss of coating between innerand outer circuit. (Estimate and record amount.) Considerable cutthrough and fraying at the inner and outer circles.  2 Severe Between25% to 50% loss of coating between inner and outer circle. Severe lossof coating at inner and outer circles. Metal substrate quite apparent. 0 Total Failure Greater than 50% loss of adhesion and coating surface.

[0090] 5. Commented and Precautions:

[0091] 5.1 The preferred approach to running this test is to establish aset of operating parameters for speeds of turntable 38 and cam 40, theoscillating amplitude, and temperature of oil 51, then vary the load ortime. Once this has been established, setting up individual testsproceeds quickly and smoothly.

[0092] 5.2 Check balance arm 34 and oscillation of balance arm 34frequently to ensure that it has not become loose and changed.

[0093] 5.3 This test can be run cold, i.e., without hot oil 51.

APPENDIX B Test Method B Resistance to Mechanical Damage by KnifeCutting and Scraping

[0094] 1. Scope:

[0095] This test simulates the cutting and scraping action of metalkitchen utensils on a non-stick coated surface. It measures theresistance to slicing through the coating by the edge of a blade as wellas resistance to sideways scraping by a blade. Therefore, the test is agood indicator of resistance to damage by kitchen utensils such as metalspatulas. The test is very reproducible, and readily distinguishesdifferences in the hardness, toughness and adhesion (especiallyintercoat adhesion) of coatings systems.

[0096] 2. Equipment and Materials:

[0097] 2.1 Mechanical scratch adhesion apparatus 30 b, such as thatshown in FIG. 4, with set of weights 44 and fixture arm 60 to hold blade62 at a proper angle to coated substrate surface 36 b.

[0098] 2.2 Steel Q-Panel blades 62 (Type QD-35), available from Q-PanelCompany.

[0099] 2.3 Timer.

[0100] 3. Procedure:

[0101] 3.1 Position test piece 64 on the center of turntable 38 ofscratch adhesion apparatus 30 b.

[0102] 3.2 Lock a new Q-Panel blade 62 into place in fixture arm 60.Make sure that panel blade 62 is in the position shown in FIG. 4.

[0103] 3.3 Load fixture arm 60 with weight 44. Typically, this weight isbetween 750 to 1,000 g. A standard weight 44 is 900 g. Lock fixture arm60 so that fixture arm 60 does not make contact with test piece 64.

[0104] 3.4 Start turntable 38. The speed should be 15-16 rpm in ananti-clockwise direction. Start cam 40 to oscillate fixture arm 60. Thecam speed should be 20-22 rpm. Release fixture arm 60 and set the edgeof panel blade 62 gently on substrate surface 36 b of test piece 64.

[0105] 3.5 Continue running the test until an agreed upon endpoint isreached. Usually, this test is run for two hours or until 10% of thesubstrate is revealed.

[0106] 4. Evaluation:

[0107] 4.1 Refer to FIG. 5. This drawing shows the motion of test piece64 at 70 and the motion of panel blade 62 at 72.

[0108] 4.2 Rate the amount of wear at Points A, B, and C according tothe scale set forth in Table III of Test Method A. The area between Aand B receives single scraping action at maximum circumferential speed.Panel blade 62 is perpendicular to the circle of rotation of test piece64. Circle A receives the second greatest scraping damage. The areabetween B and C receives double scraping action at medium to lowcircumferential speed. Circle B receives the greatest scraping action.Circle C receives cutting action with panel blade 62 running tangentialto the circle of rotation of test piece 64.

[0109] 4.3 Photograph results.

[0110] 4.4 If running a series of tests it is sometimes easier to rankthe performance to provide a relative rating of damage resistance ratherthan an absolute number rating. Wear patterns can vary, and a singlenumerical rating does not always convey the true nature of the damageresistance of the coating.

What is claimed is:
 1. A single coat, non-stick coating system,comprising: at least one binder resin (12), one said binder resinincluding at least one of amide and amine functional groups; and atleast one fluoropolymer resin (14 a), one said fluoropolymer resincapable of reacting with at least one of said amide and amine functionalgroups of said binder resin.
 2. The coating system of claim 1, whereinone said binder resin is selected from the group consisting ofpolyamideimide, polyamide, polyimide, and a combination thereof.
 3. Thecoating system of claim 2, further including an additional resinselected from the group consisting of polyphenylene sulfide, polyethersulfone, polyether ether ketone, silicone, and a combination thereof. 4.The coating system of claim 1, wherein said fluoropolymer resin (14 a)includes an additional fluoropolymer resin selected from the groupconsisting of polytetrafluoroethylene, fluorinated ethylene propylene,perfluoroalkyl, and a combination thereof.
 5. The coating system ofclaim 1, wherein said fluoropolymer resin (14 a) is a copolymerincluding vinylidene fluoride monomers.
 6. The coating system of claim1, wherein said fluoropolymer resin (14 a) is a terpolymer oftetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride,having a melting point of from about 160° C. to about 250° C.
 7. Thecoating system of claim 1, wherein said binder resin (12) comprisesapproximately 25% to 65% of the solid content of said coating system. 8.The coating system of claim 1, wherein said binder resin (12) comprisesapproximately 20% to 100% by weight a resin including a functional groupselected from the group consisting of amide and amine functional groups.9. The coating system of claim 1, wherein said fluoropolymer resin (14a) comprises approximately 15% to 60% by weight of the solid content ofthe coating system.
 10. The coating system of claim 1, wherein saidfluoropolymer resin (14 a) comprises approximately 5 to 100% by weightof the solid content of the coating system a fluoropolymer resin withvinylidene fluoride moiety.
 11. The coating system of claim 1, whereinsaid fluoropolymer resin (14 a) comprises 5% to 30% by weight vinylidenefluoride.
 12. The coating system of claim 1, wherein said fluoropolymerresin (14 a) has a melting point in the range of about 160°0 C. to about250° C.
 13. The coating system of claim 1, wherein said fluoropolymerresin (14 a) has a melt viscosity of greater than about 10³ poise. 14.The coating system of claim 1, further including a filler materialselected from the group consisting of zinc oxide, aluminum oxide,zirconium oxide, titanium dioxide, iron oxide, chromium dioxide, siliconoxide, aluminum silicate, magnesium aluminum silicate, silicon carbide,titanium carbide, silicon nitride, titanium nitride, boron nitride, andmixtures thereof.
 15. The coating system of claim 14, further includinga pigment, said pigment selected from the group consisting ofultramarine blue zeolite, channel black carbon black, and mixturesthereof.
 16. The coating system of claim 15, wherein said pigments andsaid fillers comprise approximately 0% to 45% by weight of said primer.17. A single-coat, non-stick coating system in the form of an aqueousdispersion, comprising: a binder resin (12) including at least one ofpolyamideimide, polyamide, and polyimide; and a fluoropolymer resin (14a) including a copolymer of tetrafluoroethylene, hexafluoropropylene andvinylidene fluoride monomers.
 18. The coating system of claim 17,wherein said binder resin includes an additional resin selected from thegroup consisting of silicone, polyether sulfone, polyphenylene sulfide,polyether ether ketone, and a combination thereof.
 19. The coatingsystem of claim 17, wherein said fluropolymer resin (14 a) includes anadditional resin selected from the group consisting ofpolytetrafluoroethylene, fluorinated ethylene propylene, perfluoroalkyl,and a combination thereof.
 20. The coating system of claim 17, furtherincluding a filler material selected from the group consisting of zincoxide, aluminum oxide, zirconium oxide titanium dioxide, chromiumdioxide, silicon dioxide, aluminum silicate, magnesium aluminumsilicate, silicon carbide, titanium carbide, silicon nitride, titaniumnitride, boron nitride, and mixtures thereof.
 21. The coating system ofclaim 17, further including a pigment selected from the group consistingof ultramarine blue zeolite, channel black, carbon black, and mixturesthereof.
 22. A substrate (16) coated with a single coat, non-stickcoating, said non-stick coating comprising: at least one binder resin(12), one said binder resin including at least one of amide and aminefunctional groups; at least one fluoropolymer resin (14 a), one saidfluoropolymer resin capable of reacting with at least one of said amideand amine functional groups of said binder resin; and a filler material.23. The substrate (16) of claim 22, wherein one said binder resin (12)is selected from the group consisting of polyamideimide, polyamide,polyimide, and a combination thereof.
 24. The substrate (16) of claim22, wherein said fluoropolymer resin (14 a) includes a copolymer havingtetrafluoroethylene, hexafluoropropylene, and vinylidene fluoridemonomers
 25. The substrate (16) of claim 22, wherein said fluoropolymerresin (14 a) includes an additional resin selected from the groupconsisting of polytetrafluoroethylene, fluorinated ethylene propylene,perfluoroalkyl, and a combination thereof.
 26. The substrate (16) ofclaim 22, wherein said coating is applied to said substrate by at leastone of spraying, curtain coating, and roller coating.
 27. The substrate(16) of claim 22, wherein said substrate (16) is selected from the groupconsisting of stainless steel, carbon steel, and aluminum having asurface roughened to an average roughness of about 2-5 μm (80-200microinch).
 28. The substrate (16) of claim 22, wherein said substrate(16) is aluminum etched to an average roughness of about 0.5 to 2 μm(80-200 microinch).
 29. The substrate (16) of claim 22, wherein saidfiller material is selected from the group consisting of zinc oxide,aluminum oxide, zirconium oxide, titanium dioxide, chromium dioxide,silicon dioxide, aluminum silicate, magnesium aluminum silicate, siliconcarbide, titanium carbide, silicon nitride, titanium nitride, boronnitride, and mixtures thereof.
 30. The substrate (16) of claim 22,wherein said coating further includes a pigment, said pigment selectedfrom the group consisting of ultramarine blue zeolite, channel black,carbon black, and mixtures thereof.